 Changes in your diet not only affect you physically, physiologically inside, but also mentally, how well you think, psychologically, how well you feel. But you'll never know just how good you can feel until you put it to the test and try eating healthier. Welcome to the Nutrition Facts Podcast, I'm your host, Dr. Michael Greger. You know I talk a lot about the killers in our food, but what happens when we are the food? Today we ponder the pros and cons of repelling mosquitoes with deet. The most dangerous animal in the world isn't the Great White, or the King Cobra, or lions and tigers and bears. In fact, only about 10 people die in shark attacks every year. Coming in number two is most dangerous, fellow human beings. But the worst? Mosquitoes. Literally billions of people are at risk of contracting dengue fever from mosquitoes, and hundreds of thousands die from mosquito-borne malaria every year. New threats like Zika continue to pose a global public health threat, such that the World Health Organization suggested delaying pregnancy in Zika-affected areas around the world. What's the best mosquito repellent to wear? There are products like Permethrin, a product originally derived from chrysanthemms, interestingly, that can be applied to clothes. But what about repellents you actually put on your skin? Deet is the repellent to beet, considered the gold standard of protection when it's crucial not to get bitten. It was developed back in the 1940s for use by the military. It's long been considered the first line mosquito repellent. Effectiveness-wise, 20-50% deet repellents provide up to several hours of protection. That's rubbed on the skin, though. Deet impregnated wrist bands don't work repelling mosquitoes only from areas covered by the band, which I guess you could say about non-deet impregnated wrist bands. Deet or citronella wrist bands have been clocked at working more broadly for only 12 to 18 seconds. Safety-wise, deet is considered safe even in the second and third trimesters of pregnancy and in children, as long as they're older than two months. Now, it should be noted that deet can damage plastics and synthetic materials. Therefore, care should be taken when it's used around plastic watches, eyeglasses, and synthetic fabrics. The nylon is OK, but it's been found to damage spandex, rayon, acetate, and pigmented leather in addition to plastic and vinyl. Deet is absorbed through your skin into your bloodstream, but it's cleared from your system within a few hours. Does it have any adverse effects? Deet is probably far less toxic than many people believe. Deet has a remarkable safety profile after now more than a half century of use and billions of applications. Fewer than 50 cases of serious toxic effects have been documented in the medical literature since 1960, and most of them were solved. Most reported cases of adverse or lethal events involved overuse or incorrect use of the product. Incorrect use as in chugging it to commit suicide. What's a correct usage? Read and follow all directions on the product label. Only apply to intact, non-irritated skin. Do not apply near eyes and mouth and only sparingly around ears. Always to avoid accidental eye exposure or ingestion. It can be applied to the face, but don't spray it in your face. Spray it on your hands and then you can dab on, but still avoid the eyes and mouth. Apply it to children so they don't swallow any. Just use enough to cover exposed skin or on the outside of clothing, not underneath. And then once you're back inside, wash it off with soap and water and wash any treated clothing. If you do have a reaction, stop using it, wash it off, install your local poison control center, and if you go to your doctor, bring the bottle. So which mosquito repellent works best? Well in head-to-head tests, DEET crushed it. But this was in reference to a study published about 20 years ago. Anything new on the market that won't melt your eyeglasses? We'll find out next. DEET has been considered the most effective mosquito repellent. Unquestionably, read this editorial in the Journal of Family Practice, it should be the only mosquito repellent recommended by physicians with no other repellent coming close. Given the dramatic efficacy, it's hard to concede that any other repellent would ever beat it. However, there are some rare reports of severe reactions to DEET, not to mention the fact that it can melt plastics like eyeglass frames and cell phone components, and many consumers find the odor and sensation on the skin unpleasant. Enter pachyridin. Overall, studies have shown little difference between DEET and pachyridin applied at the same dosage, with some evidence pointing to a superior persistence for pachyridin, all without the irritant, odor, and melted glasses. No wonder it got consumer reports pick for the best overall insect repellent. Note that concentration matters, their 20% pachyridin product topped the list, but at 5% it was one of the worst performing products. Any toxicity? Adverse effects, when occurring, primarily manifest it as eye irritation, redness, vomiting, and oral irritation. But of course you're not supposed to eat it or spray it in your eyes, but even unintentional ingestion was associated only with relatively minor toxicity. What about the electronic mosquito repellent gizmos? Ten studies done in all ten found that there was no difference in the number of mosquitoes landing on people with or without the gizmos, and experiments out in the field confirm no effect on preventing mosquito bites. Pachyridin was roughly based on a black pepper compound, but like DEET is a synthetic chemical. Are there any natural repellents? Of course just because something is natural doesn't mean it's necessarily safe. Strict 9 is a natural product of the Strict 9 tree, and ricin from caster beans is 10,000 times deadlier still. In fact, the top 10 most toxic poisons are all natural. But let's look at the mosquito repellent effects of about 20 essential oils compared to a placebo control group and to DEET. Five had any lasting effect at all. Peppermint and lemongrass oil were effective for 30 minutes. Spearmint and garlic oil started working, but didn't even last that long. Cinnamon oil, though, reduced mosquito attraction for one and a half hours. The remaining essential oils had no significant effect on mosquito attraction at any time point, and this includes citronella. Citronella was the most widely used repellent before DEET was invented, and it's still used today in many formulations despite inferior efficacy. At lower concentrations it may only last a few minutes, and at higher concentrations citronella can cause skin irritation. Compared to a complete protection time of six hours for DEET, citronella may only last 10 and a half minutes. Therefore citronella may be acceptable for brief exposure to nuisance mosquitoes, but it is not advised for protection if you really can't afford to get bit. Essential oils, read this, family medicine journal editorial, have no effectiveness and are not recommended. But that was before we learned about lemon eucalyptus, the only plant-based repellent recommended by the CDC, though should not be used by pregnant women or children younger than three years of age. Consumer Reports listed it as one of their top three picks warding off mosquitoes and ticks for at least seven hours. All the other botanical products they tested failed, but 40% lemon eucalyptus was shown to prevent bites for 47 hours after application for aggressive species of mosquitoes and for greater than 12 hours for less aggressive mosquitoes, a period of prevention greater than at least a 10% DEET repellent. We would love it if you could share with us your stories about reinventing your health through evidence-based nutrition. Go to NutritionFacts.org slash Testimonials, which may be able to share it on social media to help inspire others. If you'd like to see any of the graphs, charts, graphics, images, or studies mentioned here, go to the Nutrition Facts Podcast landing base. There you'll find all the detailed information you need, plus links to all the sources we cite for each of these topics. My last two books were How to Survive a Pandemic and My How Not to Diet Cookbook. Get ready this year for the launch of How Not to Age and of course all the proceeds for the sales of all my books goes directly to charity. NutritionFacts.org is a non-profit science-based public service where you can sign up for free daily updates on the latest new nutrition research with bite-sized videos and articles uploaded nearly every day. Everything on the website is free, there are no ads, no corporate sponsorships, no kickbacks, it's strictly non-commercial, not selling anything. I just put it up as a public service as a labor of love as a tribute to my grandmother whose own life was saved with evidence-based nutrition.